Our work for the next five years will be focused on the structure and function of the ribosomal RNA, and its topography within the ribosomal structure. We plan to (1) obtain the rest of the nucleotide sequence of the rrnB ribosomal RNA cistron (ca.5500 base pairs), including the structure of the 23S RNA gene, 5S RNA gene, tRNAGlu gene, promoter, termination, and RNA processing sequences; (2) deduce secondary structures for 16S and 23S RNA, using seven independent biochemical criteria to test the possible alternative structures; (3) employ RNA-RNA and RNA-protein crosslinking to gain information about the folding of 16S and 23S RNA and their spatial relationships with the r-proteins; (4) explore the mechanism of tRNA binding, especially the role of 16S and 23S RNA, using kethoxal and other chemical probes in conjunction with diagonal methods and rapid gel techniques; (5) mutagenize cloned rRNA genes, and use resulting mutant plasmids to study rRNA structure and function.